Chlorophyll is a chemical found in almost all plants and algae, and in some bacteria. It allows them to absorb light and transfer it to their photosynthetic reaction centers. This energy is used for a specific redox reaction, in which electrons are promoted to a higher energy level. This, in turn, allows for light energy to be converted into chemical bond energy. This entire reaction chain is known as photosynthesis. It generates energy needed for a variety of processes, such as growth or repair to damaged tissues in the plant. The similarities between chlorophyll and the function of blood in the human body led to its nickname of "plant blood.” It is a green pigment, and tints stems and leaves green. Chlorophyll can be used as a natural substitute for synthetic dyes in confectionery products and pasta.